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MIT reinvent the light bulb!

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MIT reinvent the light bulb!

Post by Cathovisor » Tue Jan 12, 2016 1:30 am


 
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Re: MIT reinvent the light bulb!

Post by Terrykc » Tue Jan 12, 2016 12:02 pm

An excellent idea but possibly a bit late in the day?

I wonder how long the traditional ES and bayonet cap holders will last with the decreasing use of incandescent bulbs? 

Will new buildings use different fittings from day one, better suited for smaller, lighter LEDs? (Sorry about the pun!)

Rewired buildings would see the same fittings used, in the same way that, in previous times, 5A & 15A sockets were routinely replaced by 13A ones. As the market for ES and Bayonet types diminishes, the price differential caused will accelerate the change.

This new technology, if successful, is likely to take some time to develop. Is it possible that there won't be enough suitable fittings left by the time they become widely available?

CFLs are getting much better - the slow start up of early types seems to have been eliminated, judging by the performance of more modern replacements in our house and, no doubt, LED technology will continue to improve. After all, it isn't that long since LEDs were only available in red. Green followed quickly afterwards but blue was a longer time coming - followed, of course by white.

 
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Re: MIT reinvent the light bulb!

Post by Cathovisor » Tue Jan 12, 2016 12:31 pm

I try never to read BTL comments as it makes me despair, but this one from that Telegraph piece made me smile:
Telegraph comment.png
Telegraph comment.png (5.08 KiB) Viewed 2059 times
Errr.... which one? Doubt it's fluorine or chlorine... :qq1

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Tue Jan 12, 2016 1:54 pm

There are no white LEDs. They are Blue / Violet with a yellow phosphor. The regular fluorescent tube or CFL adaptation gives far better colour rendition (best is less efficient phosphors). Achilles heel of LED is that with age it goes bluer and 10% plus losses in the electronics (even if off 12V). A fluorescent tube or CFL can use a low loss choke, though only the double D type CFL commonly uses a choke. I'm not sure of efficiency of the Electronic ballasts for CFL etc.
The Electronics on CFLs and LEDs usually fails before the actual lamp does.

For the same true area of illumination, there isn't much difference in efficiency, though LEDs work better in cold (the CFL / Fluorescent can be rather dim in cold).

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Tue Jan 12, 2016 2:00 pm

Cathovisor wrote:I try never to read BTL comments as it makes me despair, but this one from that Telegraph piece made me smile:
Telegraph comment.png
Errr.... which one? Doubt it's fluorine or chlorine... :qq1

Maybe bromine? But probably a mix. High pressure too.
The idea was demonstrated before WWII with bromine, but Wikipedia says iodine.
https://en.wikipedia.org/wiki/Halogen_lamp
They also claim Chlorine was tried in 19th C.
I'd imagine the Chlorine attacked the glass and wire supports.
You seriously don't want any mix of Chlorine and Fluorine, especially one particular compound.


The MIT research seems interesting. A halogen thermal tungsten filament has best colour rendition of any common retail lighting (Not sure how some RF excited lamps and Xenon discharge compare).

 
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Re: MIT reinvent the light bulb!

Post by Cathovisor » Tue Jan 12, 2016 2:17 pm

When halogen lamps first started appearing on motor cars, they were frequently described as "Tungsten Iodide headlights" - so I think we know what's in use there. The big problem of course was that the bulbs were usually made of quartz to resist the much higher temperatures the bulbs ran at (which in turn sparked a degree of debate about the suitability of some cars for retrofitting these bulbs - would the reflector stand the heat?) so it was implicit that the bulbs weren't to be touched because any grease from the fingers would rapidly be burnt into the surface of the bulb. Now modern filament bulbs also carry a warning that the bulbs are under pressure so don't hit them when fitting!

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Tue Jan 12, 2016 2:43 pm

It's probably mostly Iodine. Possibly with an inert gas too?

A 55W Halogen car headlamp gives more light than a non-halogen 50W, a little less heat. It's just the heat is concentrated on a smaller envelope!

BBC also reporting it.
http://www.bbc.com/news/science-environment-35284112
6.6% is actually very good as efficiency of CFL drops with low tempertaure and age, LEDs are limited by PSU, physics, yellow phosphor and thus poorer when hotter and progressively worse colour as ages.

At least Halogen bulbs are not banned, but ALL lamps over state performance on packaging (sometimes by 30%) and the Halogens are shorter life to boost efficiency. I have 2 x disc PSU inrush limiter thermistors in series (one speced is for 400W SMPSUS) in light switch in rooms with 4 x 50W Halogen and the room with 2 x 105W halogen to dramatically lengthen lamp life.
UK gets much less life from Halogen than same bulb in mainland Europe or here due to life is inversely 14th power of voltage.

 
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Re: MIT reinvent the light bulb!

Post by Cathovisor » Tue Jan 12, 2016 3:12 pm

Michael Watterson wrote:It's probably mostly Iodine. Possibly with an inert gas too?

I could well be wrong, but I think I've heard krypton mentioned in the past. Xenon of course is used in the discharge lamps used on many cars, although even these are beginning to get competition from LEDs - main advantage being dispensing with the high voltage circuitry.

 
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Re: MIT reinvent the light bulb!

Post by Terrykc » Tue Jan 12, 2016 3:53 pm

Michael Watterson wrote:There are no white LEDs. They are Blue / Violet with a yellow phosphor. 
Not so, Michael! RGB White LEDs are  available in addition to the phosphor types but, apart from the additional manufacturing cost of putting 3 LEDs in the one package, I think the low maximum intensity available from green LEDs tends to limit their efficiency and luminous output.

 
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Re: MIT reinvent the light bulb!

Post by Cathovisor » Tue Jan 12, 2016 5:01 pm

Terrykc wrote:
Michael Watterson wrote:There are no white LEDs. They are Blue / Violet with a yellow phosphor. 
Not so, Michael! RGB White LEDs are  available in addition to the phosphor types but, apart from the additional manufacturing cost of putting 3 LEDs in the one package, I think the low maximum intensity available from green LEDs tends to limit their efficiency and luminous output.

Really? Some green LEDs I've met would detach your retina!

The phosphor-type LEDs are excellent - they are now being increasingly used in television lighting and are virtually identical to their tungsten counterparts in colour rendition (very slightly bluer, I've noticed). The difference for lighting directors is that their colour temperature doesn't change when dimmed; whilst many luminaires now carry their control equipment within the fitting so need power and DMX data to function - but no dimmer room any more!

 
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Re: MIT reinvent the light bulb!

Post by Jamie » Tue Jan 12, 2016 6:19 pm

Here's what's lighting my bedroom currently...
Image
sod you EU. :aah

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Tue Jan 12, 2016 7:11 pm

Terrykc wrote:
Michael Watterson wrote:There are no white LEDs. They are Blue / Violet with a yellow phosphor. 
Not so, Michael! RGB White LEDs are  available in addition to the phosphor types but, apart from the additional manufacturing cost of putting 3 LEDs in the one package, I think the low maximum intensity available from green LEDs tends to limit their efficiency and luminous output.

RGB LEDs can do any colour TEMPERATURE simulation. They are NOT white! They are RGB, only good for LCD backlights as the colour RENDITION is ghastly, the sources are too monochromatic. The near Monochromatic R, G & B in a package is USELESS for anything other than projector lamps and LCD panels. Things that are really orange, yello cyan etc will be dark or completely wrong colour under so called White done with R G B. The Yellow phophor + Blue/Violet LED is better, but ghastly for objects predominately between Green and Blue under white light.

Colour TV is a trick. Similarly a white monochrome tube isn't too bad a light source, but good colour CRT adjusted to same colour temperature is a terribly uneven spectrum. R G B LEDs are far worse as the LEDs are closer to monochromatic Red, Green and Blue than RGB phosphors!

LEDs + phosphors can't easily do the spectrum of CFLs due to being too long wavelength, The UV LED + loads of phosphors are less efficient than CFL, and still not as good. Best compromise is yellow phosphor + blue-violet LED.

 
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Re: MIT reinvent the light bulb!

Post by Jamie » Tue Jan 12, 2016 7:15 pm

Michael, in which case NOTHING is indeed "white light" except daylight as the definiton is that of "apparently colourless light, for example ordinary daylight. It contains all the wavelengths of the visible spectrum at equal intensity."

Therefore, ANY attempt at arguing ANY artificial light source can display white light or anything remotely near is futile. :bbc Every light source beit Metal Halide, High-Pressure Sodium, Low-Pressure Sodium, Mercury Vapor, Tungsten-halogen, Xenon, Fluroescent, LEDs, or bill and ben have their own colour output in a seperate part of the spectrum.

Also, at the end of the day. Our eyes and brains interperate temperature, rendition and other factors of light in different ways. An LED television may be ghastly to some, But others may indeed prefer it much to the same that I personally prefer CRT's despite their flicker.

Science can indeed give you answers, However you do need to bear in mind each human is individual in their preferences and one cannot be told what light is "wrong".

 
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Re: MIT reinvent the light bulb!

Post by Niall » Tue Jan 12, 2016 8:00 pm

The difference is that incandescent bulbs have a continuous colour spectrum, it might not be all that even but it is continuous. As Michael says all the alternatives as far as I know emit some combination of monochromatic light to give an impression of white.

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Wed Jan 13, 2016 11:53 am

Niall wrote:The difference is that incandescent bulbs have a continuous colour spectrum, it might not be all that even but it is continuous. As Michael says all the alternatives as far as I know emit some combination of monochromatic light to give an impression of white.

Halogens are best, very like daylight.
All kinds of incandescent lamps have a smooth even spectrum, but may be red shifted compared to daylight (lower colour temperature).
CCFLs, CFLs and Fluorescent tubes have a very discontinuous ragged spectrum with gaps. Higher quality specialist tubes for shop display cabinets etc are less efficient due to a wider variety of phosphors used to fill gaps. They are still very jagged. So called White LEDs have a very narrow peak between Blue and near UV (depending on exact dope/material) and a broad hump from red to green, peaking at yellow from the phosphor, so reds and greens are less vivid, true cyans (colours between green and blue) are nearly none existent. An RGB LED simulating white is three very narrow peaks at Red, Green and blue. Only lasers have narrower spectrum than an LED. An LED is nearly a laser.

You can use a prism or a CD to see a spectrum of a lamp. Not accurate enough to see jaggedness in CFL etc, but "White" LED should be obvious, an RGB very much so.

CFLs and Fluorescent tubes can be quite good, but not good enough for serious photography or video. Search for spectrums. No LED even comes close to poor spectrum Fluorescent /CFL lamps (high efficiency CFL). The CCFL can be nearly as good as good CFL, but they are usually used as backlights, so optimised for output peaks at the desired R, G, B peaks of camera sensors and efficiency. They are superior to cheap "white" LED backlights on LCD (so called LED TV) which are yellow phosphor + blue/violet LED. High quality LCD panels (so called LED) use R, G, B, LEDs to give superior efficiency and colour map. R G B based colour displays don't have colour rendition in illumination sense, the issue is to match the peaks of the camera sensitivities to create the illusion of colour. "Primary Colours" are biological construct, not physical. Some birds are tetrachromatic as slightly are some women, but for humans the cornea/lens etc blocks UV. People with plastic lens after cataract operations may experience near UV sensitivity and TV / video feed of their garden can't then be made to match what they see.

Another article on the lamp development

http://www.theregister.co.uk/2016/01/12 ... _research/

EDIT:
Just checked an LED torch on back of CD. If you angle so red is at edge and blue at hub, you can see a dark gap near the blue. You'd need something more accurate to measure the shape of the light level from Red to Green.

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Wed Jan 13, 2016 1:22 pm

MIT work may be derived, based or inspired by:
http://phys.org/news/2009-05-regular-bu ... laser.html
From 2009
The laser process creates a unique array of nano- and micro-scale structures on the surface of a regular tungsten filament—the tiny wire inside a light bulb—and theses structures make the tungsten become far more effective at radiating light.

 
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Re: MIT reinvent the light bulb!

Post by Rebel Rafter » Wed Jan 13, 2016 1:32 pm

Hi all from RR. Has anyone ever noticed what is printed on the bases of CFL's? Have you ever noticed that the current quoted there doesn't match the power rating? For instance a 25 watt one has the current consumption quoted as about 183mA when if it really is 25 watt then surely the current should be nearer to about 100mA. So what is the real power consumption of CFL's? What power are they quoting, the consumption or the light output? I once carried out some experiments of my own with some CFL's to try and find out, I put a really low value resistor in series with several different CFL's one at a time and measured the voltage across the resistor each time and the current was more or less as quoted, thereby indicating that the power consumption was actually much higher than that quoted. Any ideas anyone? RR.

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Wed Jan 13, 2016 3:28 pm

They are allowed to quote a lower power consumption than reality due to how the testing procedure tolerances are specified. There is also issue of RMS vs peak vs average and power factor.

The light output Watts is at best 10% of power in.

 
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Re: MIT reinvent the light bulb!

Post by Cathovisor » Fri Jan 15, 2016 6:40 pm

Michael Watterson wrote:CFLs and Fluorescent tubes can be quite good, but not good enough for serious photography or video.

On the contrary; fluorescents have been used for some time in cinematography and video (in fact, I just walked past some at work) - http://www.kinoflo.com/

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Fri Jan 15, 2016 7:16 pm

Cathovisor wrote:
Michael Watterson wrote:CFLs and Fluorescent tubes can be quite good, but not good enough for serious photography or video.

On the contrary; fluorescents have been used for some time in cinematography and video (in fact, I just walked past some at work) - http://www.kinoflo.com/

Specialist tubes, not the more efficient domestic ones.

I was thinking of readily available lamps from the high street. But Halogen are still superior.

 
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Re: MIT reinvent the light bulb!

Post by raditechman » Sat Jan 16, 2016 10:08 am

Jamie said
sod you EU


The ban on incandescent domestic lamps is not just an EU issue. It applies in most major countries.
I imagine if UK were not in EU the ban would still apply.

Lets wait and see how this new lamp develops, although I have no problems using LED lamps or florescent tubes.

John

 
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Re: MIT reinvent the light bulb!

Post by Michael Watterson » Sat Jan 16, 2016 1:26 pm

Most things in UK media blaming EU would be unchanged if UK left EU. But let's not get into politics.

 
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Re: MIT reinvent the light bulb!

Post by Jamie » Sat Jan 16, 2016 2:53 pm

:zx: :zx:


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